The half life of a radioactive substance is 5 years. After x years a given sample of the radioactive substance gets reduced to of its initial value. The value of x is ______.
Answer: 20
Solution
The radioactive decay follows:
where is the number of half-lives.
Given that
Since , we have half-lives.
With half-life years:
where is the number of half-lives.
Given that
Since , we have half-lives.
With half-life years:
JEE Main · 2022 · 29 Jun 2022 · Shift 2 · Integer answer